Pomona College, Claremont, California 37 



given under the separate species will show that many of the individuals studied, and 

 practically all of these in which the mouth was enlarging, contained no food. It 

 seems hardly necessary to say in this connection that the absorption must make 

 possible this period of fasting. 



It must take some little time for the food to pass through the long alimentary 

 canal of the lar\a, since it was quite noticeable that in many of those examined in 

 which the mouth plates liad recently been shed, the caudal portion still contained the 

 mud and other contents typical of the larva and which had probably been taken into 

 the body when the mouth plates were still in place. 



The length of the body without considering the tail, remains almost unchanged 

 during transformation, but the rotund aspect of the tadpole gives way to the flatter 

 and more angular one of the young frog. The appearance of the front legs, the left 

 one coming out through the spiracle and the right one breaking through the skin, 

 as well as the shrinking of the tail are further indications of the progress made in 

 transformation. Usually the tail is almost gone before feeding as a carnivor begins. 



It is to be noticed that in the data given for the bullfrog almost every trans- 

 forming individual is reported as having swallowed some of its own cast epidermis. 

 This is true to a lesser degree of the other species, probably because the mucli smaller 

 size of such species as the tree-toad and the toad makes the rcognition of epidermis 

 in the alimentary tract of preserved specimens more uncertain. The frequent occur- 

 rence, one might say almost universal occurrence, of epidermis in transforming 

 individuals must mean frequent moulting. Doubtless this is true, especially of the 

 tail, which shrinks rapidly and might naturally shed its epidermis. That the shedding 

 of the skin takes place in the water is evidenced by the threads of Spirot/yra and 

 Zygnema often wrapped up in it as if during seizing and swallowing. 



The discussion of transformation may be concluded, then, by saying tliat it is 

 accompanied by a period of fasting during which time, in all eight species, the food- 

 getting and food-assimilating apparatus is rebuilt and changed from one suitable 

 to a form largel\ herbivorous and at least feeding only on dead animal material, 

 to one wliicli will permit of the predaceous and carnivorous habits of a frog or toad. 



PRESENTATION OF DATA FOR THE SPECIMENS EXAMINED 



In the following pages lists are given of the specimens dissected with data show- 

 ing the degree of transformation and the contents of the alimentary canal. The 

 word "stomach-content" is not sufficent here; for in many cases the stomach was 

 almost empty while the large intestine contained large amounts of food; in the case 

 of insects, passage through the digestive tract in this way had not sufficiently changed 

 many specimens to make it impossible to identify them to family at least. In the 

 data given under each species, "No." refers to the number of the specimen, "Body" 

 to the length in millimeters, measuring from the tip of the head to the base of the 

 tail; "Tail" to the length of the tail in millimeters, "Mouth" to the condition of the 

 mouth, whether that of the tadpole with the horny plates or with these shed, or with 

 the mouth enlarged; "Ali. Can." to the length in millimeters and to the condition 

 of the alimentary canal; "Fore Legs" to the presence or absence of the front legs; 

 "Lot" to the lot to which the particular specimen belonged, and "Food" to the 

 material found in the digestive tract. 



